20 BULLETIN NO. 2. 



crease by implantation, and are somewhat variable in size, being 

 usually about equal to the intervening spaces. 



Length 1{^- inches ; breadth If^ inches ; length of hinge line 

 1^ inches. 



Position and locality : Kinderhook group ? half a mile above 

 Elsah, Jersey county. 111. 



No. 2506 of the Illinois State collection. 



Collector, A. H. Worthen. 



AVICULOPECTEN CHESTEEENSIS. (sp. UOV.) 



Shell above the medium size, nearly equilateral, broadly ovate 

 or semi-circalar in outline, a little wider than long ; left valve mod- 

 erately convex, beak depressed and extending slightly beyond the 

 cardnial border. Anterior ear broken away, posterior ear small 

 and ornamented with fine lines of growth. Surface of the valve 

 ornamented with 86 to 40 radiating unequal- sized costae, the al- 

 ternate ones nearly twice as wide as the others, and all traversed 

 for more than half their length by smaller costse which become 

 obsolete before reaching the cardinal border. Traces of numer- 

 ous transverse striae are also visible where the surface of the shell 

 is well preserved. 



Length 2| inches ; breadth 2:^ inches. 



This shell is closely allied to A. Providensis, Cox, sp, from the 

 Coal Measures of Kentucky, but differs from that in its smaller 

 and more numerous costse and transverse striae. 



Position and locality: Lower division of the Chester limestone, 

 Chester 111. 



No. 2507 of the Illinois State collection. 



Collector, Mrs. J. C. Salter. 



AVICULOPECTEN SPINULIFERUS. (sp. UOV.) 



Shell of medium size, inequilateral, obliquely ovate ; left valve 

 moderately convex, and ornamented with about fifty angular spin- 

 iferous costse, each alternate one being about twice as large as 

 the others, the small ones coalescing with the large ones before 

 reaching the cardinal border. Beak moderately elevated, and lo- 

 cated about one-third nearer the anterior than the posterior ter- 

 mination of the hinga line. Anterior ear sharply triangular, about 

 half as large as the posterior, and ornamented with three or 

 more spiniferous costse similar to those on the body of the shell. 

 Posterior ear large and not clearly defined from the lateral border, 

 the spiniferous costro extending withour interruption to the car- 

 dinal border. Anterior lateral border neatly rounded from the 

 sinus below the ear to the ventral border. 



Length measuring obliquely from the beak to the basal margin 

 l\l- inches; breadth if inches; length of hinge line Ig inches, 

 posterior ear j ^ inch ; anterior ear [J inch, lliglit valve unknown. 



Position and locality: Keokuk shale, Crawfordsville, Indiana. 



No. 2508 of the Illinois State collection. 



Collector, Frank H. Bradley. 



